This invention relates generally to a method for testing a cylinder in an internal combustion engine and, more particularly, to a method for determining a weak cylinder by the response of the engine during an engine cylinder low power test.
Internal combustion engines are used to provide power for a variety of machines, including commercial on-highway trucks, earthworking and construction machines, electric power generators, and the like. Generally, it is desired to operate these machines, and hence the internal combustion engines, at a peak operating efficiency with minimal downtime due to machine or engine failure.
One type of problem sometimes encountered with internal combustion engines is the loss of power being generated and delivered due to a weak operating condition associated with one or more of the cylinders in the engine. This situation is often difficult to recognize, and may be made more difficult due to a gradual weakening of one cylinder over a period of time, thus making an awareness of the existence of a problem more difficult. As a result, it is often desired to perform periodic diagnostic analyses of internal combustion engines to ensure that each cylinder of the engine is operating at the expected efficiency.
However, these periodic diagnostic evaluations have, in the past, required downtime of the machine and the additional requirements of external instrumentation and personnel dedicated to conducting the tests. Commercial users of these machines normally cannot afford the high cost of taking machines out of use for the time required to perform this analysis. Therefore, the periodic intervals for engine evaluation may be limited to a minimum, if not eliminated completely. This limitation on checking engine performance may create additional problems, other than reduced fuel economy and lowered machine productivity, in that a minor engine problem may not be serviced until a problem with a weak cylinder becomes so noticeable that additional secondary damage occurs which would require major engine repair.
Attempts have been made to perform diagnostic analysis of cylinders of an engine during normal operating conditions. For example, in U.S. Pat. No. 5,205,152, Clarke et al. discloses (in FIG. 8 and column 8, lines 9-28) a method for evaluating each cylinder in an internal combustion engine by cutting fuel to one cylinder at a time and monitoring the resultant output of the engine. Although this method does provide a means to evaluate the condition of each cylinder in an engine while the engine is operating, it also tends to introduce undesirable crankshaft torsional stresses due to the complete cutout of a cylinder. Additional disadvantages of this method include the need for a special test mode rather than testing which is part of normal engine operation, the need for a person to initiate and monitor the test, changes to the output power of the engine during the test, and higher levels of stresses to the engine during the test.
It is desired to be able to perform diagnostic analysis on each cylinder of an internal combustion engine on a periodic basis during normal use without adversely affecting engine operation.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention a method for determining a condition of a cylinder in an internal combustion engine having a plurality of cylinders is shown. The method includes the steps of reducing an amount of power being generated by a first cylinder, increasing an amount of power being generated by each of the remaining cylinders, monitoring a condition of the engine, and determining the condition of the first cylinder in response to the monitored condition of the engine.